This acknowledges "too many connections" and "max user connections"
errors in MySQL and propagates the error up the chain so we can notify
the user and return the correct HTTP code.
This puts the verbiage more in line with what the feature does, and
leaves room for other moderation controls in the future.
NOTE: this includes no backend refactoring, which may be confusing. We
should rename things to fit ASAP.
Ref T661
This renders all requests for that user's posts, collections and related
ActivityPub endpoints with 404 responses.
While suspended, users may not create or edit posts or collections.
User status is listed in the admin user page
Admin view of user details shows status and now has a button to activate
or suspend a user.
